Drilling out broken screws

laika

laika

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What's the secret?

Excuse the question: I've only owned power tools since buying a boat. It's a huge palaver for me and takes hours yet other people seem to manage it in minutes. There seems to be three possible factors:
1. Drill. I've got a rubbish 16.8v one I was given (I think it originally came from Aldi), but it doesn't appear to be slipping
2. Drill bit. I'm using HSS titanium coated drills from halfords which say they're suitable for metal (incl. steel) (What does "HSS" even stand for? High Strength Steel?). Do I need something else tipped with some exotic substance?
3. Technique. Frankly I've tried most options. Fast, slow, small drills, larger drills, lots of pressure, not much pressure.

What's the secret to quickly and efficiently drilling out old screws with broken heads?
 
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laika said:
What's the secret?

Excuse the question: I've only owned power tools since buying a boat. It's a huge palaver for me and takes hours yet other people seem to manage it in minutes. There seems to be three possible factors:
1. Drill. I've got a rubbish 16.8v one I was given (I think it originally came from Aldi), but it doesn't appear to be slipping
2. Drill bit. I'm using HSS titanium coated drills from halfords which say they're suitable for metal (incl. steel) (What does "HSS" even stand for? High Strength Steel?). Do I need something else tipped with some exotic substance?
3. Technique. Frankly I've tried most options. Fast, slow, small drills, larger drills, lots of pressure, not much pressure.

What's the secret to quickly and efficiently drilling out old screws with broken heads?
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What material are the screws you are trying to drill made from?
 
rotrax said:
What material are the screws you are trying to drill made from?
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Err....how do I tell? Looks like "metal" with "rust" on the parts I haven't been holding the drill against. Definitely not chocolate.

It's also not aluminium or it wouldn't have fused with the aluminium it's pushed through. I'll also take a punt that it isn't something developed by NASA to be harder than an impossibly hard thing: it's just a mismatched screw which has been rather sloppily stuck through a hole in a hatch frame where a rivet presumably once was, pointy side out. I intend using my shiny new pop riveter when this screw is out of the way.
 
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If you can flatten off the remaining portion of whatever is sticking out,dab the centre as close as is possible to give yourself a decent chance,obviously the larger the object you can start wi.th a decent size drill.Make sure you are using good quality sharp drills,slow and steady increase drill size until just below actual size,then pick out remainder.Probably most important point is dabbing the centre of the objectas close as possible to actual centre.
 
fergie_mac66 said:
and what is the material around it .drilling SS out of alumin can be perplexing
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Per post #3, aluminium.

Right then. Cobalt drill. Lubricate. start small. go slow. I was already aiming for the centre but this hasn't worked out as well as I'd like. Just broke another skinny drill on it. Will get the bus to B&Q to investigate what they have in cobalt. Now why doesn't Danny Dyer do something useful like a one-off show on Britain's Hardest Drills?
 
Be very careful with screw extractors they can break and then you are in real trouble, been there done that, I had to get an engineering company to remove both screw and extractor with a spark erosion machine.
 
laika said:
(What does "HSS" even stand for? High Strength Steel?)
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HSS stands for High Speed Steel, as in steel bit that runs at "high" speed. Note that this is NOT as fast as the drill can spin, far from it, but relative to other boring technique it is pretty quick.
Drilling is a cutting action, not grinding, if set up properly you should get 2 even spirals of swarf which get long enough to take your eye out (so wear goggles). The bit should not get hot, cutting oil will help with this. If it squeaks you are going too fast or not pushing hard enough, if the bit breaks you pushed too hard or not inline.

I read, up thread, to dab the centre, I call that centre punch. Always start with something (centre punch/ dab...) else the bit will walk. Often use a much smaller bit for a pilot hole, and even use a few graded sizes of bot to gently enlarge the hole.
If at all possible get the work piece to a drill press.
 
laika said:
Per post #3, aluminium.

Right then. Cobalt drill. Lubricate. start small. go slow. I was already aiming for the centre but this hasn't worked out as well as I'd like. Just broke another skinny drill on it. Will get the bus to B&Q to investigate what they have in cobalt. Now why doesn't Danny Dyer do something useful like a one-off show on Britain's Hardest Drills?
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As said above, a quick tap with a centre punch if possible should create a small depression which will help locate a small (1mm or 2mm) cobalt or HSS bit. You have to keep the bit very much in line with the drill with a gentle pressure and a slow speed plus lubricant. These drills snap easily as you've found so you do have to avoid any lateral stress. Once the small bit has started to bite into the metal, you can replace it with one a mm larger. Once you get up to 3mm and 4mm you can use a bit more pressure as they are stronger.

Even stainless steel is not too difficult if you take it a step at a time.

I find reverse thread extractor usually do the trick but you do have to have a good depth and width of hole to allow them to get a safe grip and self-centre. If it's a small stud or screw, say 5mm or less, using small extractors is risky and you might as well drill the whole thing out as mentioned above.

Richard
 
There is a lot to be said for drill bit quality too. if it says made in China then do yourself a favour and throw it in the bin. You're going to throw it in the bin anyway but by doing it first you save yourself the hassle and disappointment of putting it in the chuck and attempting to drill with it.
Get yourself a proper drill from a reputable manufacturer. centre punch the broken bolt. if it has an uneven surface then give it a quick file (if you can) to make centre punching easier. then run a pilot hole. Smaller drill bits generally run a bit quicker than bigger ones. then step up to a drill size that will leave you about a mm of broken bolt diameter, drill that through then get an appropriate size Easyout style screw extractor and run that in anti clockwise until it catches then continue anti clockwise until it comes out. If you don't have proper cutting compound or coolant to lubricate the operation use a bit of engine oil or engine oil and water shaken up into an emulsion.
But rule #1: Save your money and visit a proper trade counter or engineering supplier and buy a quality set of bits or at least the sizes you need. I'm a huge fan of Cromwell tools but that's just because they're local branch is ten minutes away from me. Any good engineering supplier will suffice.
 
davidwf said:
Be very careful with screw extractors they can break and then you are in real trouble, been there done that, I had to get an engineering company to remove both screw and extractor with a spark erosion machine.
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I will second this. Also been there, done that. Have sworn off screw extractors. 99% of the time if the screw wouldn't come out with a screwdriver then it isn't coming out with the extractor either. When (not if) the extractor breaks in the screw then you are screwed yourself.
 
Seashoreman said:
Just done exactly that and am having the weekend off to think it over.
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The last time I broke off a screw extractor (and I mean last time in both senses of the word as I will never again use one) I found one way to get it out myself. Get a tungsten carbide bit, either a grinder size bit or you can get small ones for a Dremel tool. They aren't cheap. USD$12-$15 for a Dremel bit or $30-$40 for a 1/4" grinder bit but they will cut through most anything.
 
Many thanks to everyone for such a complete and detailed set of answers. Trade counters aren't open til tomorrow and it's probably worth investing in some decent drill bits for this. On the few occasions I've done this before it's been such a faff and adding proficiency in this would be a great addition to the skills locker. Thanks again and I shall report back how a naïf has learned from forum wisdom.
 
Fascinating thread. I am disappointed to learn reverse cutting screw extractors do not work as they are brilliant for removing screws from bone when the hex head is not longer a hex!

TudorSailor
 
tudorsailor said:
Fascinating thread. I am disappointed to learn reverse cutting screw extractors do not work as they are brilliant for removing screws from bone when the hex head is not longer a hex!

TudorSailor
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They are generally fine for removing screws with damaged heads from wood, fiberglass and most other softer materials and seldom fail in those applications. But when you get to a SS screw frozen into an aluminum piece (like winches mounted on a mast) or steel screws rusted into an engine block in my experience they will break far more often than they work.

Best is to soak the screw with a good penetrating oil, repeating and letting sit for a few days. Kroil and PB Blaster seem to be the ones recommended by the experts. For really tough jobs heat, may help. If you can get it, an oxy/acetylene torch with a fine flame. I recently read of another trick. One mechanic takes a set of jumper cables from a 12V battery. Connect one end to the frame or body of the piece holding the screw then touch the other cable to the tip of the screw. Expect a good spark when you do this. Hold it on a few seconds, 5-6 should do it, no more than 10. That should heat up screw a lot and break the bond between the screw and the surrounding metal.

Plan to try this on a couple of SS screws stuck in the aluminum frame of a hatch. Will report back on how it goes. Hopefully I don't set things on fire.
 
Proper drill bits

One of the marine professionals "over here" highly recommends the drill bits from Norseman / Viking. Same bits under two different brand names. Not cheap but he claims they eat through stainless parts better than the fancy coated bits. Here's a link and no, I have no interest in the company and get no commissions or free bits from them.

http://www.ebay.co.uk/itm/Norseman-...-LOOK-44170-/251329052545?hash=item3a8460ff81
 
I too have used tapered reverse direction screw extractor bits with limited success. The problem stems from the fact that if there is only a small thickness of the broken piece left in place there is every chance that the tapered extractor will spread the remnants and make it even more difficult to remove. Because of this I use the parallel fluted extractors.
 
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